1. Field of the Disclosure
The present disclosure relates to a backlight unit, an assembly structure of which is modified to minimize the thickness of a bezel forming the external appearance of a liquid crystal display device and to prevent optical defects, such as light leakage, and a liquid crystal display device using the backlight unit.
2. Discussion of the Related Art
Recently, as flat panel display devices used in personal computers, portable terminals and monitors of various information equipment, liquid crystal display devices, plasma display devices, field emission display devices and light emitting display devices are on the rise.
In such a flat panel display device, a display panel displaying an image is seated on a separate guide bracket or panel guide, and is assembled with the inside of a front cover or a back cover forming the external appearance of the flat panel display device. Particularly, in the case of a liquid crystal display device, a liquid crystal panel itself cannot emit light, and thus a backlight unit is further provided on the rear surface of the liquid crystal panel and is assembled with a panel guide and a back cover.
In order to meet consumer' various demands for stylish design and the light-weight and thin-thickness trends, development of a liquid crystal display device which employs an edge type backlight unit including light sources formed of light emitting diodes to supply light on the side surface of the backlight unit and has the minimum thickness of a bezel is required.
In a conventional liquid crystal display device in which a front cover or a top case is formed in a designated size other than a thin bezel, a sufficient distance between a plurality of light sources and a diffusion plate to convert and diffuse an optical path from the respective light sources is obtained. Thus, optical defects due to diffusion sheets may be prevented even if the diffusion sheets are disposed directly on the diffusion plate. Particularly, when the sufficient distance between the plural light sources and the light diffusion plate is obtained, light leakage or formation of light beams generated by the rib shape of a prism sheet from among the diffusion sheets disposed directly on the diffusion plate may be prevented.
However, if the thin bezel is formed, a distance between the plural light sources and the diffusion plate is inevitably narrowed, and thus it may be impossible to prevent optical defects generated by the shape of diffusion sheets when the diffusion sheets are disposed directly on the diffusion plate. Particularly, when the sufficient distance between the respective light sources and the diffusion plate is not obtained due to the thin bezel, optical defects such as light beams or light leakage due to the rib shape of the prism sheet from among the diffusion sheets occur, thereby causing a defect in image display and greatly lowering product reliability. If the bezel surrounding the edge of the front surface or the frame of a liquid crystal panel has a thin thickness, a distance between plural light sources and a diffusion plate is inevitably narrowed. Thereby, when optical sheets are disposed directly on the diffusion plate, optical defects cannot be prevented by the shape of the diffusion sheets. Particularly, when the distance between respective light sources and the diffusion plate is not sufficiently secured by reducing the thickness of the bezel, optical defects due to the rib shape of the prism sheet from among the diffusion sheets occur and thus cause image display defects.